Despite the high prevalence of lumbosacral transitional vertebra (LSTV), little is known about the biomechanics of this condition. In addition, as previous studies have focused solely on symptomatic and elderly LSTV patients, the relationship between LSTV and congenital or developmental spinal stenosis remains uncertain. In the present study, the spinal canal diameters were measured in young subjects in whom degenerative changes have not yet become significant. Seventeen young adults with LSTV and 24 normal controls were included in this study. The spinal canal sagittal diameter, interpedicular distance, interfacet distance and lateral recess diameter were measured using CT scans. There was no significant difference in the measured values between the two groups. In conclusion, the results indicate that there is no relationship between LSTV and a congenitally narrower canal.